1. Field of The Invention
This invention relates generally to the manufacture of netting or screening mesh and particularly to screening which is intended to be incorporated in apparatus or devices designed to accomplish sifting out finer materials which are intermingled with coarser materials, as for example, ores.
2. Description of The Prior Art
Prior art screening which has been particularly constructed for sifting apparatus and other uses in industry has generally been formed of interlaced or woven metallic strands. When used to sift certain materials, such as ore or other hard substances, as such materials are passed across a prior art screened area, the noise produced may be objectionably loud. Such objectionable noise can be produced either by the material bouncing across the metallic strands of the screen, or by such material causing the contacting wire strands to rub against each other.
Another objection to metal screening of the prior art is that the metallic wires can abrade the material being passed over the screening where, in some instances, such abrasion may not be desired. If the material being sifted is very hard, however, the metal screening itself may become abraded. In addition, such prior art metal screening may required a considerable amount of time on the part of service personnel to mount, remove or repair the metallic screening in sifting apparatus installations. Further, such screening can become plugged or deformed with respect to the materials being screened, thereby adversely affecting the efficiency of the sifting process by, for example, permitting an undersized piece of ore to be retained on the screen or permitting an oversized piece of ore to pass through the screen where deformation has occurred. In addition, it is well known that prior art metal screening does not ordinarily last for a long period of time when it is subjected to intensive use in a sifting process, being subject to rust or other deterioration, not only through such use, but even when placed in storage. Lastly, metallic screening is ordinarilly heavy and necessarily adds greatly to the weight of sifting frames or mountings so that it may be inconvenient to handle.